The present invention relates to a heat generating member cooling structure and a drive unit.
When an electric motor is used as a driving power source of a vehicle, the electric motor requires an inverter for controlling the electric motor and an ECU or the like for controlling the inverter. The inverter and the like are each connected to the electric motor via a power cable. Thus, it is possible to position these elements in appropriate places away from the electric motor. However, for the sake of convenience during the installation of theses elements into the vehicle, these elements may be arranged to be integrated with a drive unit that has the electric motor built therein.
The heat resistance temperature of the inverter and the like is currently lower than the heat resistance temperature of the electric motor. Thus, when the inverter and the like are positioned so as to be integrated with the drive unit that has the electric motor built therein, it is necessary to have an arrangement for blocking the heat that is directly transferred from the electric motor to the inverter and the like in order to thermally protect the inverter and the like. In addition, because the temperature of the inverter and the like increases due to their own heat generation, it is necessary to cool down the inverter and the like so that they are kept below their heat resistance temperatures.
To cope with this circumstance, a drive unit that has a cooling structure for cooling down an inverter as well as an electric motor has been proposed (for example, see International Publication No. WO 2004/025807). In the cooling structure included in the drive unit disclosed in International Publication No. WO 2004/025807, a coolant space is formed between a heat releasing surface that is thermally connected to an inverter and an opposing surface that is positioned opposite the heat releasing surface and is thermally connected to the drive unit case. A plurality of heat releasing fins are provided within the coolant space such that they are positioned parallel to one another and stand so as to protrude from the heat releasing surface on the inverter case side toward the case surface on the drive unit case side. An inter-fin passage through which the coolant flows is formed between every two of the plurality of heat releasing fins that are positioned adjacent to each other. In this type of cooling structure, the coolant that is supplied by a coolant pump into the coolant space flows through the plurality of inter-fin passages that are positioned parallel to one another. With this arrangement, it is possible to cool down the inverter via the heat releasing surface and also to cool down the electric motor via the opposing surface.
In conventional heat generating member cooling structures that are used for cooling down a heat generating member such as an inverter like the one described above, a configuration has been proposed in which heat releasing fins are formed to stand from a heat releasing surface by cutting and raising the heat releasing surface that is thermally connected to the heat generating member with the use of a cutting tool (for example, see Japanese Patent Application Publications No. JP-A-2005-142247 and No. JP-A-2005-254417).
In the conventional heat generating member cooling structures disclosed in Japanese Patent Application Publications No. JP-A-2005-142247 and No. JP-A-2005-254417, the plurality of heat releasing fins are formed so as to be positioned parallel to one another by cutting and raising, a number of times in succession, the heat releasing surface so that there is a small distance between the heat releasing fins. Thus, inter-fin passages, each of which has a small width, are formed so as to have a small distance there between. In this configuration, it is considered that the heat transfer area of the heat releasing fins is enlarged, and the level of heat releasing performance is improved.
Another heat generating member cooling structure has been proposed in which a plurality of heat releasing fins that stand from the heat releasing surface are positioned parallel to one another. An inter-fin passage through which coolant flows is formed between every two of the plurality of heat releasing fins that are positioned adjacent to each other. Further, each of the heat releasing fins is formed so as to have a meandering shape that has a plurality of bent portions along the direction in which the coolant flows (see, for example, Japanese Patent Application Publication No. JP-A-2006-100293).
In the heat generating member cooling structure disclosed in Japanese Patent Application Publication No. JP-A-2006-100293, by arranging the plurality of meandering-shaped heat releasing fins so as to be positioned parallel to one another, a meandering-shaped inter-fin passage having inflection portions that inflects the flowing direction of the coolant is formed between every two of the plurality of heat releasing fins that are positioned adjacent to each other. In this configuration, it is considered that the heat transfer area of the heat releasing fins is enlarged, and also the level of heat releasing performance is improved by inflecting the flowing direction of the coolant at the inflection portions of the inter-fin passages so that turbulence is promoted in the flow.